1. Field of the Invention
The present invention relates to a tape cassette for use in a video tape recorder (VTR).
2. Description of the Prior Art
Front-loading video tape recorders have a cassette insertion slot defined in the front panel thereof for loading and unloading a tape cassette therethrough. The loaded tape cassette is retained by a cassette holder that is positioned within the video tape recorder housing adjacent to the cassette insertion slot. Thereafter, the cassette holder is moved along a predetermined path to bring the tape cassette to a position near recording and reproducing heads. It is therefore desired that the cassette holder be of a structure capable of reliably retaining the tape cassette and the tape cassette be of a structure that can easily be held by the cassette holder.
FIGS. 1 through 3 of the accompanying drawings show a conventional cassette holder. In FIGS. 1 through 3, the cassette holder has a bottom plate 1, a pair of side plates 2A, 2B extending upwardly from opposite side edges of the bottom plate 1, and a pair of top plates 3A, 3B extending from upper edges of the side plates 2A, 2B toward each other parallel to the bottom plate 1. Presser springs 4A, 4B are mounted respectively on the top plates 3A, 3B. As shown in FIG. 3, a conventional tape cassette 5 comprises a lower casing half 6, an upper casing half 7, and a front lid 8. When the tape cassette 5 is inserted into the cassette holder in the direction indicated by the arrow D1, the presser springs 4A, 4B are elastically displaced to a position P1, and the tape cassette 5 is retained in position between the presser springs 4A, 4B and the bottom plate 1 under biasing forces from the presser springs 4A, 4B.
If the biasing forces of the presser springs 4A, 4B are too strong, they tend to damage the tape cassette or prevent the tape cassette from being loaded smoothly into the cassette holder. If the biasing forces of the presser springs 4A, 4B are too weak, the tape cassette would possibly be left behind the cassette holder when the cassette holder is moved toward the recording and reproducing heads.
To avoid the above shortcomings, it has been customary to lower the speed at which the cassette holder moves and also to keep the biasing forces of the presser springs 4A, 4B within a small allowable range. However, such a conventional practice is disadvantageous in that the speed at which the tape cassette is loaded is low and the cost of manufacturing the loading mechanism is high.
Another problem is that the biasing forces of the presser springs 4A, 4B decrease overtime due to aging, resulting in progressively smaller retentive forces with which the tape cassette is retained in the cassette holder.
Various efforts have been made to lock tape cassettes securely in cassette holders. However, all of the prior attempts have failed to solve the above problems because they rely on frictional forces against a flat surface of the tape cassettes to retain them in place in the tape holders.